What to consider when applying N in-season to corn

0 downloads 136 Views 277KB Size Report
For further information on. Monty's products and to find your local Monty's dealer, contact Joe Koll, Monty's Plant. Foo
16 www.FarmProgress.com ● May 2015

The Farmer

Crops

What to consider when applying N in-season to corn Key Points

Crop Rx RADITIONALLY, most Minnesota corn growers apply the majority of nitrogen fertilizer preplant, either in the fall or anywhere from a few days to a few weeks before planting. Because of a greater potential for N loss from excess precipitation that typically occurs in early spring, more growers are interested in waiting to apply nitrogen until after the crop is growing, or at least to split the application so some of the N is applied when the crop is growing. Splitting the N application for dryland corn does not normally increase the maximum yield level, says Fabián Fernández, University of Minnesota nutrient management specialist. However, with split applications, growers may see an economic optimum yield level with less nitrogen.

T

N application options Sidedressing N at the time of crop uptake

■ To reduce loss, more growers wait to apply N until after the crop is growing. ■ Sidedressing N offers farmers more flexibility. ■ Soil injection, dribbling between rows, broadcasting before rain reduce losses. helps minimize N losses. Another advantage of sidedress application is that it allows growers to determine if a full rate is needed, based on yield potential. For instance, a poor stand or poor growing-season conditions may reduce the yield potential and the need to apply the full N rate. In extreme cases, when it is getting late to replant, a decision may be made to change crops. This decision can be less painful if the full N rate was not yet applied. However, management plans that include split nitrogen or sidedress-only applications also have their potential risks. Potential drawbacks include insufficient precipitation to move the fertilizer into

Sponsored by Monty’s Plant Food

Extra Insurance Ensures the Highest Yields. Charlie Hubbard

Springtime has arrived. But instead of warmth and sunshine, many parts of the country are faced with cooler temperatures and wet soil conditions. As a grower, what impact does this have on planting and the prospects for a successful season? Adverse soil conditions can range from too cool (below 55 degrees) to too damp. This causes sub-surface, side-wall compaction and ultimately results in a wide range of nutrient deficiencies. “Growers who plant too early will most likely see nutrient deficiencies,” says Charlie Hubbard, agronomist for Monty’s® Plant Food Company. “Deficiencies in manganese, phosphorus and zinc will slow the crop’s emergence and overall growth, leading to a loss of yield.” It is far easier and more costeffective to address nutrient deficiencies at planting, rather than trying to rescue a crop

in-season. That’s why growers who understand Hubbard’s perspective are analyzing their soil and assessing their planting conditions now – and preparing their fields to deliver maximum yield. Microhance handles nutrient deficiencies at planting. Farmers who apply a starter in-row on the seed, or even 2x2, should consider using a micronutrient package such as Microhance®. The combination of essential nutrients could make the difference between early success and constantly trying to catch up. Microhance can also be foliar or soil applied and is designed to provide nutrients at any stage of growth, which in turn helps maximize yield potential. It includes boron, iron, manganese, sulfur and zinc, all of which enhance plant metabolism. Microhance also offers plants an organic form of

nitrogen to enhance green-up and growth. “Adding Microhance at planting is like giving yourself extra insurance for the season,” says Hubbard. “Why not ensure that you will get the highest yields possible?” For further information on Monty’s products and to find your local Monty’s dealer, contact Joe Koll, Monty’s Plant Food’s Product Consultant and Sales Support Representative for North Dakota, South Dakota and Minnesota, at (701) 205-5486 or [email protected]. For more information on Monty’s Plant Food products, please visit www.montysplantfood.com.

Success you can see.®

© 2015 Monty’s Plant Food. Monty’s®, Success you can see®, and Microhance® are registered trademarks of Monty’s Plant Food Company. 43252D 05/15 DAFR TFMR

the root zone; not being able to apply N on time if the soil is wet, and then having to use high-clearance equipment to make the application; fertilizer being injected between rows later in the season, resulting in root damage; damage to the foliage resulting from ammonia escaping in the case of anhydrous ammonia applications; and leaf burn or discoloration if UAN or urea products are broadcast over the crop. Often, fine-textured soils can experience nitrogen loss through denitrification in wet years with preplant applications. While a sidedress application could be beneficial to mitigate the N loss potential, these soils are also difficult candidates for sidedressing in wet years.

When to apply N at sidedress “Sidedress can be done anytime between planting and tasseling. However, under Minnesota conditions, research continues to show that delaying applications past V6 to V8 results in yield reduction,” Fernández says. Normally, up to the V6 development stage, corn does not require a lot of nitrogen, and sufficient N is typically available from mineralization, starter fertilizers, weed-and-feed applications or small amounts of preplant N applications. However, Fernández explains, after about V7-8 corn, N uptake is rapid, and delaying application past that time often results in yield reduction.

Which N to apply According to Fernández, injection into the soil and dribbling the nitrogen fertilizer between rows are the best ways to sidedress because these two forms of application can reduce volatilization of urea and protect the crop from foliar damage. “When using anhydrous ammonia, watch soil conditions to ensure proper closure of the knife track to avoid foliage damage from free ammonia,” he says. “If injection or dribble is not a possible option, broadcast nitrogen applications would be the next-best method.” Urea granules will have the least impact on leaf burn compared to UAN, ammonium sulfate or ammonium nitrate. If a grower uses a dry product, Fernández recommends applying it when leaves are dry to minimize adhesion of the product to the leaves. Fernández cautions farmers to keep in mind that urea is subject to volatilization if rain does not fall within a few days after the application. Within 10 days of application, as much as 30% of broadcast urea can volatilize if not incorporated by rain. This volatilization loss of surface-applied urea can be reduced by the addition of Agrotain

to the urea before application. According to Fernández, UAN solutions can be an excellent source of sidedress nitrogen if applied using a toolbar that injects UAN 2 to 3 inches deep. UAN also can be surface-applied by fitting the applicator with hoses or tubes that direct the solution away from the corn plants. If a grower is going to spray UAN over the top of growing corn, expect some leaf burn, Fernández says. Damage to 6-inchtall plants will be minor, while foliage burn to V4 plants will be more sustainable. Growers can reduce this potential leaf burn by applying UAN when temperatures are cooler, diluting the UAN with water, or applying it when rain is expected in the near term. For plants to be safe and to reduce emotional stress from seeing burned corn leaves, rates of nitrogen with broadcast UAN over the top shouldn’t exceed 30 pounds N per acre when corn is V4 or taller.

How much N If N is being managed for a split application and there has been low potential for N loss from earlier applications, a nitrogen rate calculator (extension.agron.iastate.edu/ soilfertility/nrate.aspx) should be used to determine the total nitrogen application (preplant plus sidedress). Fernández adds that if substantial N loss occurred during the earlier part of the growing season, determining how much nitrogen should be added during sidedress to compensate remains a difficult task. “The pre-sidedress nitrate-nitrogen test [PSNT] was developed in Iowa and works well under some conditions there and in other states,” Fernández says. “In Minnesota, the utility of the test is limited. The only reliable information the test provides is that there is no need for nitrogen if the test is greater than 20 parts per million. But if it is below that, the test is not calibrated for our soils to tell us how much N should be applied.” Fernández advises growers that if substantial N loss occurred earlier in the season from the preplant application but yield potential is still high, adding 20 to 40 pounds N per acre to the total nitrogen previously planned for sidedress should be sufficient. Source: Minnesota Agricultural Fertilizer Research and Education Council The Minnesota Agricultural Fertilizer Research and Education Council funds various nitrogen research projects that explore tools to sustain crop production and reduce potential environmental effects from crop nutrients. To learn more about the results of the council’s research, visit mnsoilfertility. com.